The advent of recombinant DNA technology has led to the molecular cloning of a large number of coding sequences or genes from diverse cell types. In order to study the function of these genes or to produce the products encoded by such sequences, these genes are inserted in expression vectors under the control of appropriate regulatory sequences. This transfer of the expression vector into a eukaryotic or prokaryotic host cell generally results in the expression of the encoded product which can be subsequently purified. Large-scale production of many gene products is particularly important in cases where such products are of medical or industrial value.
However, notwithstanding the advances in gene expression, certain coding sequences do not readily produce their products in stable form. For example, expression in E. coli of recombinant proteins could be problematic particularly for proteins with trans-membrane domains or extensive hydrophobic sequences. Moreover, recombinant proteins may not contain the N-terminal amino acid residues with the appropriate codon bias. Thus, there remains a need for improved materials and methods for the expression of recombinant proteins.